Thermal Imaging Page 2
— February 2002
By Ben Ellison
Some Like It Hot
|Part 2: IR Detectors|
Unlike light amplifiers, IR detectors can "see" targets in total darkness or when they have bright lights behind them. They can even see through smoke and, to a lesser degree, fog (moist air degrades IR energy). A material that IR does not travel through well is glass. Hence, the lenses of thermal imagers are made of the rare and very expensive metalloid germanium. That's one reason why even the more modest units cost in the $10,000 to $20,000 range.
Of course there's more to the technology than a lens, as a look at two HotEye models will illustrate.The HotEye 3x is a six-pound handheld that has the feel of a portable spotlight. It uses a ferroelectric IR sensor--sometimes called second generation--to push a greenish 320- by 240-pixel image to its four-inch LCD. It comes standard with a manually focused 50mm lens, which yields an 18-degree horizontal field of view and can supposedly detect a man at a distance of 1,600 feet. (It's indicative of IR imaging's roots in military targeting and surveillance that "range of human detection" is a standard unit of comparison.) The unit also has two-to-one digital zoom, much like a video camera, which this technology resembles much more than it does a monocular.
The HotEye 109 is meant to be fixed on a cabin top or tuna tower and is encased in a standard ACR 100 spotlight housing, using the ACR jog stick for pan and tilt. This seems like a clever idea in terms of aesthetics and ease of repair; D&B's Gravely reports that he's working on a similar arrangement with the manufacturer of traditional chromed megayacht spotlights.
The model 109 uses a third-generation microbolometer IR sensor, small enough to fit in the ACR case and also more solid-state and rugged. It only produces a 160- by 120-pixel image, but Gravely says that its increased sensitivity (.001 degree, 10 times better than that of the ferroelectric) more than makes up for the decreased resolution. The unit outputs to a standard NTSC video lead, and thus the user can feed the signal into any video-capable monitor. It comes standard with a 100mm lens, nine-degree field of view, and human detection to 2,800 feet. Both models sell for about $15,000, and D&B can provide either with alternate lenses and other customization.
D&B is a small company that has only been in existence for a couple of years, but it has high hopes. Gravely acknowledges that Raytheon opened the door to thermal imaging in the marine market a few years ago but eventually dropped out; he thinks the key to success is targeting large boats with a few good distributors who thoroughly understand the products. While Raytheon's Infrared division no longer builds marinized thermal imaging units, it is responsible for the sensor in the HotEye 3x and is busy in the currently active military and public safety markets. One might hope that the growing use of the technology would drive manufacturing costs downward, but there is the opposing dynamic of rare germanium.
Price aside, thermal imaging appears to be another valuable electronic aid to navigation. Gravely likes to refer to one of D&B's favorite customers, professional sportfishing captain Eddie Herbert, whose comments are posted on the company's Web site: "We have had a HotEye on the new Reel Tight (80-foot Merritt) for four months now, and it has already allowed me to navigate around debris and objects in the water that our top-of-the-line [70-mile] radar couldn't pick up. Just the other evening we avoided a collision with a small 16- or 17-foot open boat running at night without lights."
If Herbert is also using his HotEye to check out the ladies around the marina, he's not saying.
D&B Technology Phone: (407) 647-7500. Fax: (407) 647-7505. www.hoteyenow.com.
ITT Industries Phone: (800) 448-8678. Fax: (540) 362-4574. www.ittnightvision.com.
Ben Ellison has been a delivery captain and navigation instructor for nearly 30 years and was recently the editor of Reed's Nautical Almanacs.
This article originally appeared in the January 2003 issue of Power & Motoryacht magazine.